Sunday, August 30, 2015

More Preparations for the Rotor and Mast Installation

Since this is Part 11 you can well see that I have abandoned Roman Numerals and counting in Latin. Too bad Miss Bushnell!

This is the third day since the concrete was placed (not poured) and so it is OK now to remove the forms (yes I waited only one day). The three days is to allow the concrete to set enough to proceed with the follow on work. I can say this is not the best placing of concrete I have done but it is "good enough" for this install. The first thing I wanted to do was a "fit check" of the rotor assembly. This is where you get that sinking feeling that the anchor bolts are in the wrong place or may have shifted during the concrete placement. Well I am happy to report that the rotor plate assembly fits on the anchor bolts and you can see that below. I wear a size 10 shoe and you can see that as a reference point in the photo. (So OK I could have cropped the photo and my shoe would disappear but this does give you a size reference.)

Preparing the Mast Assembly for Installation

I must share that the SpiderBeam mast is quite well made as you would expect nothing less coming from Germany. The form, fit and function rate high marks. One operation must be done by the customer and after an explanation from the Customer Support Representative I can see the "why".

There are a whole series of additional adapter pieces beyond the basic mast. In my case I purchased the 10 Meter Heavy Duty mast and along with the mast I bought the rotor adapter module that installs in the base as well as the top section adapter that is used with their other product the Spider Beam. The basic mast bottom section is too large to fit in the typical rotor and therefore the adapter section essentially consists of short section of pipe with a larger diameter on one end about 15 CM long that inserts inside the mast bottom section and a comparable length of a smaller diameter that will fit inside the U bolts that attach the mast adapter to the rotor. Actually the short section of pipe is made of aluminum and has a singular diameter. Over the fatter end a material similar to PVC pipe is slipped over the pipe so the net diameter of the fatter section will fit inside the main mast. This PVC sleeve is bolted to the pipe using counter sunk bolts.

From the bottom of the PVC sleeve measuring about 11 CM is a through hole that will accept a 5/16 inch bolt. The purpose of this hole is to provide an anchoring of the mast to the adapter. Enter the first small problem -- there is no matching hole in the mast base section. This is where the customer is required to accurately drill that hole so that a 4 inch long 5/16 inch bolt can be passed through the mast and adapter plate which will prevent the situation where rotor is rotating but the mast doesn't move. It also serves the purpose that if the rotor has a brake lock any wind forces on the beam will not move the antenna. A single bolt provides an important function.

At this point you would ask why doesn't the mast assembly already come with a hole drilled at the right location. Well that seems like a reasonable assumption from a customer --hey the mast can be bottom rotated and the adapter (quite well made) is factory provided so why no matching hole in the mast.

Well I am thinking back to when I had a NIB 1966 yellow Volkswagen and to my surprise there was no hood lock and within a week my spare tire was stolen --and might I add there was no spare tire lock. So when I purchased a new spare tire, at the same dealer where I bought the car, the sales person said you better purchase the spare tire lock. So I said give me one and being in a hurry since I was on my lunch hour, I simply locked the spare tire and the lock inside the car.

Later that evening when I went to install the spare tire lock I laughed out loud and my first words were "German Engineering". The spare tire lock consisted of a piece of chain, a large bolt and a padlock. The install entailed removing a bolt which attached part of the body to the frame located behind the spare tire. After removing this bolt you passed the longer kit bolt through the end of the chain and installed it in the vacant hole. Then placing the spare tire in its location you ran the chain through one of the lugs and next put the padlock on the chain. So the same question --why didn't this come like that from the factory --the cost was $13.

The answer from SpiderMast Customer Support was that few masts are sold to be rotated at the bottom as most masts are used in portable operations and are turned using the Armstrong Method. (ie hand rotation). I also was told that many of the masts are used for applications other than ham radio and therefore not rotated. So to have masts with and without holes would involve multiple part numbers and since the usage with bottom rotators is small -- the task is left to the customer. I am sure that was the same answer for the spare tire lock -- German Engineering!

The thought just occurred to me --any chance the guy who designed the spare tire lock now works for SpiderBeam?
﻿

How to drill a straight hole through the mast?

So OK the customer has to drill the hole. This is where you spend considerable time noodling (my term for thinking) the problem. There are at least three issues with the first being you only want to drill through the bottom section. With the mast nested literally all of the sections are in the hole location with the mast retracted. So the mast sections above the bottom section must be pulled out a bit so that you are only drilling the bottom section. [This was a caution from Customer Support --so others must have drilled through all of the sections.]

In looking at the adapter section a fit check in the rotator with the adapter installed it was clear that there should be about 1/8 inch clearance so that the PVC sleeve will extend about 1/8 inch below the mast. Why? Because there is just enough of the bottom section to fit within the jaws of the rotator (Yaesu G450) thus if you made the mast align with the bottom of the sleeve there may be interference with the top of the rotator housing. This is just to give you some breathing space. So allowing for this I decided the center of the hole through the mast should be about 10.5 CM. I placed a dot (magic marker) on the mast section at 10.5 CM and then placed the mast adapter near the hole and saw that the center of the adapter when aligned with the proposed hole would give the 1/8 inch clearance at the bottom. So we are ready for the next step.

To assure that the hole is drilled properly several things must happen. First you want the mast section to be "captured" so that when you are drilling there is no movement of the mast. This is easily done using four piece of scrap wood. I happen to have a small box of cut off pieces of 2X4 and this is a perfect size. So Ok I am about to put several nails in the top of my homebrew wooden workbench. Starting with two pieces of the cut off 2X4 pieces, I temporarily nailed them about 12 inches from the front edge of the bench and these are spaced about 4 foot apart. Next I laid down the mast along the length and marked the position of the other two blocks as they were butted up against the mast and then installed the last two wood blocks. These four block form a "crib" assembly to keep the mast from moving around while your drill.

The next step involves placing the mast assembly in the crib holder and finding the mark at 10.5 CM. Before drilling align that mark so it is square on the top dead center and so the mark should visually appear equidistant between the two pieces of 2X4. The final hole size is 5/16 so you will need a 5/16 inch drill bit at least four inches long. DON'T start the drilling process with this size instead you want to be "stealthy" initially starting with a 1/16 inch bit which essentially is a pilot hole. The using four or 5 sizes of drill bits each progressively larger drill the hole to size. Slow drill speeds are best and KEEP the drill vertical!

Now with one hole completed we are ready for the second hole. We start by inspecting the first hole by looking inside the mast section from the open end and evaluate if there are any burrs or other debris. This foreign matter can be easily removed using a long screwdriver with a thin blade. The next step involves placing the adapter assembly inside the mast and aligning the hole in the adapter with the hole in the mast. Now insert your drill into the first two aligned holes and carefully feel the drill bit seating in the second hole in the adapter. The adapter is now serving as a drill jig. I should mention that I placed a small square of plastic material about 1/16 inch thick between the underside of the bottom mast section and the workbench top so when the drill bit clears the metal, the plastic acts as a backstop to prevent drilling a 5/16 inch hole in the top of my workbench. With all in place and keeping the drill vertical slowly begin drill the second hole. This process worked perfectly and the holes are properly aligned and square with the world. Below are some photos of the finished assembly.

Critical Success Factors!

Measure 40 times and Cut Once.

Use the proper tools

Slow Drilling and proper hold down of the part being drilled

Check your work and noodle through each step

Pete N6QW

Friday, August 28, 2015

Placing the Concrete Base

We are victims of our past experience! Upon graduation from college (BSEE) I had to serve four years in the US Navy Civil Engineer Corps. That scholarship from the US Navy entailed a large payback -- four years of my life. During that four years I got to operate as DX from Midway Island (then KM6) but unfortunately no operation from South Vietnam during my two trips there.

As with all industries, workplaces or even the military there is certain acceptable and respected common language. Much of the construction work of the "Seabees" involved concrete, and the proper terminology was "placing concrete" not "pouring concrete". The real subtle difference was that placing had an air of precision whereas pouring sounded like a "random spilling out" that literally went everywhere. So for my project, obviously involving precision and the "knack", I placed the hand mixed concrete into the homebrew form.

Don't get ahead of yourself -- allow three days of cure time before removing the forms and at least week before adding any load bearing structure. (Well I waited 1 day before removing the forms.)

A lot of effort was expended in assuring the form was level and that the anchor bolts were in the proper position. The bolts in the right position was accomplished by having the baseplate attached to the form during the pour. The leveling as another matter especially since the concrete shrunk a bit after setting. Anticipating this problem I insured enough thread was available so that I could have a nut on the underside of the L Bracket and thus enable a precision leveling using the nut much like a jack screw.

The Placing Sequence

Tribal Knowledge Tips

Wait seven days to assure the concrete is fully cured before placing any heavy load on the base.

Spray the bolts with WD-40 before placing the concrete -- the last thing you want is concrete in the bolt threads

Spray WD-40 on the bolts while awaiting the concrete to cure. This prevents them from rusting.

Once the final leveling is done then apply a "coax seal" to the bolts so that they don't rust.﻿

Pete N6QW﻿

Tuesday, August 25, 2015

Building the Concrete Form for the Base Mounted Rotator ~ Updated 2X

Today we will cover the construction of the temporary wooden structure that will provide the form for the concrete base. Our initial calculation was that the reinforced concrete base would be about one foot cube with a portion above ground and the remainder below grade. While that seems sufficient there are other critical dimensions which include the actual area of the top surface.

The US Tower base mounting plate is essentially triangular since it is intended to be mounted within a triangular steel tower. My selection of the RP-3 (the smallest) is identified as "fitting" within a 10 inch top section thus we have approximate dimensions, likely the triangle altitude (known a "h") being close to 10 inches --well it is something less than that. The baseplate assembly, L brackets and anchor bolts are shown below, and were described in 9a.

At times it is the "practical" that drives the final solution/configuration. I had purchased two pieces of 1X4 pine each four feet long with intent of using these for constructing the concrete form. This is where I go nuts -- a 1X4 is not actually 1" X 4" but something less than those dimensions --but the four foot long was good. Thus if I made each side of the form 16 inches long that would be a total of 64 inches. Three saw cuts of one piece of the 1X4 would yield three sides each 16 inches long and a 16 inch cut of the second piece would give the fourth side. I offset two of the sides by approximately 1 inch (actually to avoid a knot on one of the pieces) and given that the 1X4 is less than one inch along one of the dimensions my picture frame box has internal dimensions more akin to a rectangle than a square, which is OK.

The final size internal size of the frame is 13 X16 X 3.5 inches. This equates to about 0.42 Cubic Feet of concrete which says the hole will have about 0.6 Cubic Feet of concrete. If we looked at a hole of about 9 inches deep and 12 inches in diameter that is slightly less than 0.6 Cubic feet. Thus we now have our dimensions for the base

Some math here and we can calculate the cubic area of the rectangular area and then determine the depth of hole so that we end up with a foot cube of reinforced concrete.

The outfall of the second piece of the 1X4 by four feet long was cut to form two pieces which straddle the picture frame box. The rotor base plate will be bolted to these two pieces and the two pieces anchored to the picture frame during the placing of the concrete in the form and the hole in the ground. Bottom line ~ this process results in the rotor baseplate assembly being placed squarely in the center of the concrete base at the proper height. When the concrete is cured the baseplate is unbolted from the form and the anchor bolts are in the exact position they need to be. I am a bit ahead of my self here.

[As an aside by having enough of the threaded portion of the anchor bolt be above the top of the concrete, it would be possible to have two nut assemblies on each bolt. One nut would be on the bottom side of the L bracket and the other (with a washer) on the top side. Such an arrangement could enable precise leveling of the baseplate assembly as the nuts underneath could provide three points of precision adjustment so that the baseplate is absolutely flat.]

Stepping back I temporarily placed the two pieces of wood that will straddle the form on top of the form. I should note that one of the piece was cut so that it would exactly straddle the form being net with the outer dimension. Why? Well as it turns out when the rotor base plate is affixed to the form one of the mounting holes will be equidistant from each side. So by finding the center of that piece of wood a 1/2 hole drilled at that location will properly align with the hole in the L bracket affixed to the base plate. We now have accurately located one of the mounting holes smack in the center of the form.

The remaining two holes of the baseplate are "in line" with each other. Here having the length exactly the width is unimportant. Thus I simply found the center of the 4 inch dimension of the 1X4 and drawing a line approximately 10 inches log aligned that length with the center of the two remaining holes. A quick scribe of the inside diameter of those two holes on to the line on the board with a felt tipped pen gave me a drilling template for the second piece of support wood. Once the three holes are drilled into the wood, the assembly complete with rotor mounted can be placed on top of the wooden form. Since one of the boards aligns with each side and since that mounting hole is in the middle we need only slide the assembly along the form until there is an equal amount of space on either side of the rotator along the other dimension. Pre-drilling of the straddle boards enables once the "center" location is found to simply screw the rotor assembly to the form. Use a total of 8 screws, two at each end so the assembly is rigid.

When you reach this point you should have an assembly that looks much like what you see in the photos below. (Additional Photos added of the completed assembly -- the anchor bolts are upside down just for these photos so the form for the concrete lies flat on the driveway.)

Having the rotor on the baseplate is important for the next phase which will entail placing a portion of the mast in the rotator assembly. Thus the baseplate, rotator and partial mast will be taken to the outside location where the antenna will be located. Once at that location, the assembly will be moved around a bit to determine the exact final location. My design not only entails the use of the baseplate assembly; but also a house bracket sleeve bearing. We know the proximate location of the base location but now we want to conduct a fit check so that when the base is anchored in the ground the mast with sleeve bearing is a proper distance from the house and rotates feely within the sleeve bearing. We will now cover that part of the process.

Monday, August 24, 2015

Case Zero -- How it Started

On August 23rd, 2015 I had cause to do an Internet Search on one of the most popular electronics magazines that started in October 1954. Oddly enough it was called Popular Electronics. In that issue I spotted an advertisement for one of the very early transistors that was available to electronic enthusiasts. Enter the Raytheon CK722 and you can see a snip of the ad below. Actually I had been using a CK722 prior to this ad --I must have been about 11 or 12 years old at the time and my use was as an audio amplifier for one of my crystal sets. Here you see the ad for building an electronic timer. Imagine what you could do with a solid state timer back in 1954.

Keep in mind the scientists at Bell Labs had invented the transistor a scant six years earlier. From a lab to the consumer in such a short period of time was simply amazing in 1950! Think about it -- there had to be a wholesale development of manufacturing techniques to mass produce transistors. Building one in a lab is a huge task, whereas building thousands of within spec transistors on a line is a whole different problem.

Raytheon manufactured a line of "pencil type" and sub-miniature vacuum tubes many which started with a CK designation like the CK7588. I suspect the CK722 nomenclature was simply a carry over from the vacuum tube part numbering system.

The CK722 came in a cool blue case with a red dot on the side which designated the collector as the three leads were inline. It was a PNP device so biasing and grounds were always a bit tricky --- the collector goes to ground!

I am pondering if when the CK722 hit the streets that there were those same "experts as we see today" who said --- "Well those will never work in homebrew radios, the phase noise is terrible and nothing lights up and glows". Very likely if there were email reflectors in 1954 those "experts" would proclaim "Don't use the CK722 because I heard the specs are no good -- the Ft is only 2 MHz and the phase noise is awful and they are PNP devices and on and on."

Well some of us simply ignored those naysayers and enjoyed this wonderful new technology! Nothing much has changed since 1954 --we still have those who only look to find fault with any new technology. One only needs to tune in to the chatter from today's naysayers who essentially have only looked at the spec sheets and state the Si5351 is unsuitable for use in our beloved ham rigs. Too bad they never have built anything but only parrot what they have heard.

Thursday, August 20, 2015

Photos of the RP-3 Base Plate, L Brackets and Anchor Bolts

* Current Antenna Moved ~ Staying on the Air During Construction

Work began in earnest today on assembling some of the major support structures. The use of Simpson Products L Brackets has greatly facilitated the build. The brackets come pre-drilled and one of the holes aligns perfectly with the RP-3 base. An opposite hole is enlarged to 1/2 inch to accommodate the anchor bolts. This was easily done on my Sears pedestal mounted drill press. About 20 Minutes of total work. The hole size in the RP-3 and the Simpson L Bracket is 1/4 inch so no additional drilling required there. Just for grins --with shipping the RP-3 cost nearly $100. The L Brackets and Bolts were cheap --about $12 with the Stainless Steel bolts and nuts for the RP-3 Plate to bracket assembly.

August 21 ~ Moved the current antenna about 3 feet to open an area for construction of the new concrete base. This area will be suitable for this antenna in the permanent setup as it will enable working the lower bands plus have the beam for the higher bands. See the last several photos in this grouping.

Wednesday, August 19, 2015

Project Update

I have become great friends with the local UPS delivery man assigned to my route. He keeps dropping off packages and religiously inquires about the status of my beam antenna project. So the blog readers I am sure would also like to know the current status. Essentially the rotor mechanism will be located at the base and the entire mast and beam will rotate.

The Configuration

Diagrammatically the antenna installation will look like the sketch below:

Starting with the base which will be 1 foot cube of reinforced concrete using rebar this will provide a platform to anchor the rotator and vertical mast. The rotator will sit on a US Tower RP-3 Base Plate which is elevated approximately 3inches from the top of the base using commercial L brackets from Simpson Products. The L Brackets are anchored into the concrete using three 1/2 Inch by 8" long anchor bolts.

The Yaesu Model G450 (good for 10 Sq. Ft. of wind load) is bottom mounted on the US Tower RP-3 Plate Mounting assembly which has been elevated 3 inches so the control cable connector clears the concrete base. Spiderbeam sells adapter sections for the top and bottom of the mast. At the bottom section one is used to provide a smooth transition from the rotor to the mast. A similar section is employed at the top of the mast to facilitate mounting in the boom to mast bracket.

Two sets of guy wires that are strategically located along the vertical mast assembly keep the mast assembly vertical. SpiderBeam recommends the use of a special material for the guy wires which evidently have some sort of magical properties. In addition I am adding a house bracket to steady the assembly at about the 9 foot level and this assembly is nothing more than a section of PVC pipe. I am of the opinion this sleeve bearing will assist in absorbing any side load torque as a result of rotation.

The Mosley Beam model MP-32, itself is a two element tri-bander which is custom built. The Forward Gain is slightly better than 3 DB on 20 Meters and has a Front to Back Ratio of 20 DB. The driven element is from a TA-32 which can take the legal limit and the other element is from a TA-32 Jr. This enables the beam to have a lighter overall weight yet be able to take the legal limit. I have a homebrew 3CPX1500A7 amp built for 20 Meters and I wanted to be able to use that amp without worrying about smoking the beam!

The beam is yet to arrive but in several days I will start on the foundation. Unfortunately I must take down my current antenna and that will put me off the air for a short period of time.

Monday, August 17, 2015

The Mystery Is Solved!

As a recap, in my prior post I was just starting to investigate the use of Arduino's that could be embedded into homebrew test gear. There are many programs floating around and many incredible, and might I add, sophisticated pieces of test equipment that can be built employing the Arduino. Many of these are in Altoids Tins.

But I simply wanted to learn how to generate and display data beyond push that there and pull this here. Thus I thought a simple display of a sine wave would be an easy entry for me to learn about how to generate the data and more importantly how to display the data. I should confess that my days of learning about trigonometric functions was 6 decades ago and thus I can claim that many of my brain cells have died along the way so I am missing some critical pieces of information. Which I was.

The plot shown in Part I are not sine waves! They look like a sine wave because I wanted so badly for them to look like a sine. Here is why they are not and I must thank Greg a ham down in VK land for providing the key to unlock the Gordian Knot!

First an excerpt from Purple Math: [It all has to do with Degrees, Degrees Minutes Seconds (DMS) and Radians. The real eye opener was Radians.]

"Why do we have to learn radians, when we already have perfectly good degrees? Because degrees, technically speaking, are not actually numbers, and we can only do math with numbers. This is somewhat similar to the difference between decimals and percentages. Yes, "83%" has a clear meaning, but to do mathematical computations, you first must convert to the equivalent decimal form, 0.83. "

Thus my equations simply plugged in x as a numerical number form 14 to 320 as in sin(x). My failure was to understand that the Arduino only works with radians. Massimo Banzai in his book on Getting Started with Arduino clearly states that the values for sin(x) must be in radians.

Greg provided me two lines of code to try in the sketch which actually does this conversion and of course it involves the use of Pi or more specifically Pi/180 which equals 0.01745329252. Making those changes results in a curve that looks like this. Now that is a sine wave! Thanks Greg!

The next photo fills in the area under the curve with hundreds of red lines.

Here is the revised code and note these two changes:

const double deg2rad = 0.01745329252;

y = 50*sin(deg2rad*x);

/* From N6QW using the 240 X 320 TFT Color display
This is to test displating graphical information such as you would have with test instrument

Saturday, August 15, 2015

More uses for the Arduino -- Test Equipment

There is always something on the bench! While I await some critical antenna parts still to come and a few parts I need for the two SSB transceivers, I thought I would turn my attention back to some investigations with the Arduino Nano coupled with TFT Color Displays.

I am amazed at how many sophisticated homebrew measuring devices (many fitting in Altoids tins) are showing up in YouTube videos and on websites. Among these are Scalar Network Analyzers, Digital SWR Bridges, Audio Test Equipment and on and on.

In some of my own efforts I figured out how to add a moving bar S Meter to the bottom of a color display so that up until S9 the bar was one color and beyond S9 another color. Thinking that was pretty cool my attention turned to how would you add real time plots to a color display such as you might have in checking out a homebrew crystal filter (I know this is what a SNA does). But I wanted to see what makes things tick.

So my first thought was how to display a Sine Wave. We have two variables X and Y, where we can represent that y = sin(x). Fortunately the Arduino has built in math functions and so it is a simple matter to set a range of values for X and then have the Arduino calculate the Y values. Along the way we can add some axis' (ordinate and abscissa) and plot centerline.

As usual I thought all you needed to do was to set up the Arduino for the color display and write a couple of math equations and you are there. WRONG!!!!!! It took me nearly two days to figure out how to display a simple sine wave. You can see that below.

The problems I ran into was that I specified 320 points (width of the display) for x starting at point x =14 so that it would fit within the axis. Well that netted multiple traces. By trial and error I found that if you only used "x" at every 5 points that you got the plot below. Anything more or less gave a screwed up plot --Inexplicable is a really good word. Since the top of the display is considered y = 0 you must offset every value by + 120 (1/2 of 240 which is the number of vertical blocks) to place the plot in the middle of the screen. So then I thought this plot consists of rectangle data points, what does it take to "connect the dots" with lines. That never did work BUT I was able to create a plot similar to what you might see in a "two tone audio test" which is shown in the second photo. Below that is the sketch wherein I used Arduino 1.0.5 -- I do have 1.6.3 on a different machine.

So email me any thoughts or suggestions. If you know what you are doing, it is probably a pretty simple thing to homebrew your own test equipment --unfortunately I don't know what I am doing!!!!

Pete N6QW

This is the code I am using (it is OK to laugh).

/* From N6QW using the 240 X 320 TFT Color display
This is to test displating graphical information such as you would have with test instruments

Monday, August 10, 2015

More Surface Mount as Applied to a New 20M SSB XCVR

Peter Parker VK3YE is probably one of the most prolific ham radio homebrewer's and you only need to look at his YouTube channel and you will be well convinced. One of his creations is called the Knobless Wonder. Basically Peter has built a simple SSB transceiver using crystals in the 40M ham band and by doing so has eliminated the need for a local oscillator. The 7 MHz BFO serves as the main frequency determining element and thus becomes essentially a single channel SSB transceiver. Brilliant idea, Peter! This keeps the circuitry simple and power consumption low. So why not?

I had thought about duplicating that project and I think Peter's crystals were in the 7.150 MHz range. That would be ideal. Alas I was unable to find those crystals from US distributors but did purchase some cylindrical crystals at 7.2 MHz from Digi-Key. Somehow I don't think those are going to work too well and 7.2 Mhz here on the left coast (California) is a major net frequency. My milli-watts would quickly be swallowed up by the big guns. But I did really like his architecture.

That led me to a slight twizzle where I would use a 9.0 MHz filter and I have in the junk box crystals at 5.185 MHz and 5.238 MHz and there may even be others in the 5.15 to 5.35 MHz range lurking in the dark corners. So those two crystals would give me a SSB signal on 14.185 and 14.238 MHz. Now we are cooking. (Just checked and I have a 5.068 MHz for the CW portion of the band).

So why not use most of Peter's architecture only put the radio on 20M. BTW a Google Search will turn up schematics for the Knobless Wonder. This led me to a board layout that was 6 Inches long by 2 Inches wide. See below. What is not on the board is the 5.0 MHz LO (2 crystals) and the final RF amplifier, TR switching and the LPF. A similar board is now in the works just for those items.

The build will be mostly Surface Mount and the 6x2 size was done with a thought of making it like a Walkie Talkie. If this works out with the two channels there is a possibility of adding some VXO capabilities and perhaps even an Arduino driving an AD9850.

Saturday, August 8, 2015

New Radios in the Queue!

While I await some of the beam parts to arrive I have taken up building (or should I say rebuilding) some new radios. The two new builds are SSB transceivers with one being on 40 Meters and the second on 20 Meters.

Beginnings of a new 40M SSB Transceiver.

The 30M CW Transceiver is Sacrificed!

In 2013 I was convinced to write an Article for QRP Quarterly that would center around a 30M CW transceiver complete with narrow filter and even an RIT. I built that project wrote the article and even had two QSO's with the radio. After having taken some nice photos for the article the radio was put into the back of the closet. That seemed a good place for the project seeing as I had no emails of inquiry and despite having some nice features no one was interested in building it. Previously I had another CW article only this one was for a 40M CW transceiver. Again not much interest.

The most interest has come from my SSB radio projects and the recent LBS series of articles is testament that most new to homebrewing want to yak and not key. We have received over 100 emails about the LBS and we know for a fact that many are under now construction. Need I say more. The hobby has room for all sorts of interests and in fact I find the SSB radios to be more of challenge to design and build than the CW ones. But to each is own.

One of my bents is to reuse circuit module blocks -- if something works then why reinvent the wheel. In the course of building the LBS, the ZIA and LBS-II it suddenly came to me that many of the blocks I would have to build where sitting in the 30M CW transceiver and since that had been all but abandoned -- a ready source of modules. The LBS has the pre-driver, driver and final stage. The ZIA ended up with the bidirectional amplifier module and the LBS-II has some of the knobs, pots and relays. Thus the sacrifice of the 30M CW transceiver was taken in earnest.

One module still intact was the mainboard which had the 30M BPF, RxTx Mixer stage (TUF-1) two bilateral amplifiers which used BF991 Dual Gate MOSFETs, the 5.0 MHz CW Filter, the Product Detector was an NE602 and the audio amp was a 2N3904 with an LM386 --and it even had a FET silencer on transmit. This main board with some modification looked like a perfect start of another 40 Meter SSB transceiver.

The 30 Meter BPF consisted of two 42IF123 Back to Back IF transformers that are nominally set to 10.7 MHz --a slight tweak to the cores put those on 30M. If you add a 68 PF Cap to each tuned winding and change he coupling cap between the IF cans to 4.7 PF --this will tune to 40M (Just like in the LBS). A quick installation of the three caps now moved the filter to 40M. The four pole 5.0 MHz filter was fairly narrow and useless for SSB. I pulled out those parts. Several years ago I experimented with building a 6 pole 5.0 MHz SSB Filter using the AADE design software. When I built it, there was a question in my mind that it worked. Throwing caution to the winds I temporarily "haywired" it in the circuit. Surprise, Surprise -- it works very well and so made a permanent part of the board. The NE602 will have to be replaced and I plan on using a homebrew DBM with a surface mount BFO/CIO.

The original 30 Meter CW transceiver used a varactor tuned heterodyne VFO and that enabled easily adding the RIT. None of that old school crap in this new radio. Having a few AD9850 DDS modules in the bin, I suited up an Arduino Pro-Mini as the controller and now had a chance to use a 8X2 cool blue display. What a great addition to even older radios. Now we have a nice stable LO signal for SSB.

I should add that the Dual Gate MOSFET bilateral amps are based on the work of Ron Taylor (G4GXO) and while have the gain fixed by applying 8 VDC to Gate 2, you could just as easily add AGC and/or ALC to these devices -- so lots of possibilities. I have actually done this is several other radios using this same bilateral circuit.

I have taken some videos of the receiver in action and when finalize the edit will upload those to youtube